1. Field of the Invention
The present invention relates to a turbine moving blade, a turbine stationary blade, a turbine split ring, and a gas turbine provided with these elements.
2. Description of Related Art
Conventionally, gas turbines have been used widely in various fields as power sources. The conventionally used gas turbine is provided with a compressor, a combustor, and a turbine, and is constructed so that after air is compressed by the compressor and then is burned by the combustor, a high-temperature and high-pressure combustion gas is expanded by the turbine to obtain power. For the gas turbine of this kind, a larger increase in combustion gas temperature (turbine inlet temperature) has been intended to enhance the energy efficiency. In recent years, a gas turbine having a combustion gas temperature as high as about 1300xc2x0 C. has been developed, and further a gas turbine having a combustion gas temperature of about 1500xc2x0 C. has been proposed.
As described above, since the combustion gas having a temperature as high as 1000xc2x0 C. or higher is introduced into the turbine for the gas turbine, various members such as a turbine moving blade, a turbine stationary blade, and a split ring, which are provided in the turbine, are made of a heat resisting alloy such as inconel. On the surfaces of these various members, a thermal barrier coating is provided to increase the heat resistance. The basic construction of these various members will now be described by taking the turbine moving blade as an example.
FIG. 10 is a sectional view showing an example of a conventional turbine moving blade. A turbine moving blade 101 shown in FIG. 10 has a platform 102 and a blade portion 103 erecting on the platform 102. With respect to the turbine moving blade 101, combustion gas is caused to flow in the direction of the arrows in the figure. The surface of the blade portion 103 and a gas path surface 104 extending in the gas flow direction of the platform 102 are covered with a thermal barrier coating 105. The thermal barrier coating 105 is composed of a topcoat 106 and an undercoat 107. The thermal barrier coating 105 constructed as described above serves to restrain heat conduction into the platform 102 and the blade portion 103.
However, the conventional turbine moving blade constructed as described above has a problem in that the thermal barrier coating 105 deteriorates and peels off in the vicinity of peripheral edge portion of the platform 102. The high-temperature and high-pressure combustion gas collides at a high speed with, for example, an upstream-side end face 108 perpendicular to the combustion gas flow direction indicated by the arrows, of the outer peripheral faces of the platform 102. Therefore, the thermal barrier coating 105 deteriorates and peels off first in the vicinity of the upstream-side end face 108. Likewise, the combustion gas collides at a certain degree of high speed with a downstream-side end face 110 perpendicular to the combustion gas flow direction (indicated by the arrows in the figure) of the platform 102, the collision being caused by vortexes etc. produced in the turbine. Therefore, the thermal barrier coating 105 deteriorates in the vicinity of the downstream-side end face 110, and in some cases, there is a fear of the thermal barrier coating 105 being peeled off. Moreover, the problem of deterioration and peeling of thermal barrier coating is also seen with a shroud of turbine moving blade, a shroud of turbine stationary blade, a turbine split ring, and the like.
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a turbine moving blade, a turbine stationary blade, and a turbine split ring which are capable of restraining the deterioration and peeling-off of a thermal barrier coating easily and surely, and a gas turbine capable of enhancing the energy efficiency by increasing the temperature of combustion gas.
As defined in claim 1, the present invention provides a turbine moving blade comprising a platform having a gas path surface extending in the combustion gas flow direction, and a blade portion erecting on the platform, the gas path surface of platform being coated with a thermal barrier coating, wherein the thermal barrier coating is formed so as to go around from the gas path surface of platform to at least a part of the outer peripheral face of the platform.
In this turbine moving blade, in order to increase the heat resistance, the gas path surface of platform is coated with the thermal barrier coating composed of an undercoat and a topcoat. Conventionally, the turbine moving blade of this type has a problem in that the thermal barrier coating deteriorates and peels off in the peripheral edge portion of the platform, especially, in the vicinity of the upstream-side end face and the downstream-side end face which are perpendicular to the combustion gas flow direction. For this reason, the inventors carried on studies earnestly to restrain the deterioration and peeling-off of the thermal barrier coating, and resultantly found the fact described below.
In the conventional turbine moving blade, the end face of the thermal barrier coating is flush with the outer peripheral face (for example, the upstream-side end face and the downstream-side end face) of the platform. Therefore, in the vicinity of the peripheral edge portion of the platform, the undercoat of thermal barrier coating is not covered at all and is exposed. For this reason, for example, in the upstream-side end portion of the platform, the high-temperature combustion gas directly collides head-on with the undercoat, which has a lower heat resistance than the topcoat, at a high speed, so that the deterioration and peeling-off of the whole of the thermal barrier coating are accelerated. Also, in the downstream-side end portion of the platform as well, the combustion gas caused by vortexes etc. produced in the turbine collides at a certain degree of high speed, so that the deterioration and peeling-off of the whole of the thermal barrier coating are accelerated.
In view of such a fact, in the turbine moving blade in accordance with the present invention, the thermal barrier coating is formed so as to go around from the gas path surface of the platform to at least a part (at least any of the upstream-side end face, the downstream-side end face, and a side end face) of the outer peripheral face of the platform. Thereby, in a region in which the thermal barrier coating is caused to go around to the outer peripheral face, the outside surface of the thermal barrier coating, that is, the surface of the topcoat is made substantially parallel with the outer peripheral face of the platform. Therefore, the combustion gas can be prevented from directly colliding on-head with the undercoat of the thermal barrier coating at a high speed. Since the thermal barrier coating is caused to go around to at least a part of the outer peripheral face of the platform in this manner to make it difficult for the combustion gas to collide directly with the end face of the thermal barrier coating (end face of undercoat), the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the platform can be restrained easily and surely.
In this case, it is preferable that a step portion be formed in at least a part of the peripheral edge portion of the platform, and the thermal barrier coating be formed so that it goes around to the step portion and the end face thereof is in contact with the upper face of the step portion.
By causing the thermal barrier coating to go around to the step portion formed in the peripheral edge portion of the platform and by bringing the end face of the thermal barrier coating into contact with the upper face of the step portion, the undercoat of the thermal barrier coating is not exposed to the outside in the vicinity of the step portion. Therefore, in the above-described construction, the undercoat of the thermal barrier coating can be completely prevented from being exposed to combustion gas in the vicinity of the step portion. As a result, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the platform can be restrained very surely.
As defined in claim 3, the present invention provides a turbine moving blade comprising a platform, a blade portion erecting on the platform, and a shroud provided at the tip end of the blade portion, a gas path surface extending in the combustion gas flow direction of the shroud being coated with a thermal barrier coating, wherein the thermal barrier coating is formed so as to go around from the gas path surface of shroud to at least a part of the outer peripheral face of the shroud.
In this turbine moving blade, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the shroud provided at the tip end of the blade portion can be restrained easily and surely.
In this case, it is preferable that a step portion is formed in at least a part of the peripheral edge portion of the shroud, and the thermal barrier coating be formed so that it goes around to the step portion and the end face thereof is in contact with the upper face of the step portion.
As defined in claim 5, the present invention provides a turbine stationary blade comprising a pair of shrouds each having a gas path surface extending in the combustion gas flow direction, and a blade portion held between the shrouds, at least either one of the shrouds being coated with a thermal barrier coating, wherein the thermal barrier coating is formed so as to go around from the gas path surface of shroud to at least a part of the outer peripheral face of the shroud.
In this turbine stationary blade, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of at least either one of the shrouds provided at both ends of the blade portion can be restrained easily and surely.
In this case, it is preferable that a step portion be formed in at least a part of the peripheral edge portion of the shroud, and the thermal barrier coating be formed so that it goes around to the step portion and the end face thereof is in contact with the upper face of the step portion.
As defined in claim 7, the present invention provides a turbine split ring having a gas path surface extending in the combustion gas flow direction, the gas path surface being coated with a thermal barrier coating, wherein the thermal barrier coating is formed so as to go around from the gas path surface to at least a part of the outer peripheral face.
In this turbine split ring, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion can be restrained easily and surely.
In this case, it is preferable that a step portion be formed in at least a part of the peripheral edge portion, and the thermal barrier coating be formed so that it goes around to the step portion and the end face thereof is in contact with the upper face of the step portion.
As defined in claim 9, the present invention provides a gas turbine for producing power by expanding a high-temperature and high-pressure combustion gas by using a turbine stationary blade and a turbine moving blade, wherein the turbine moving blade comprises a platform having a gas path surface extending in the combustion gas flow direction, a blade portion erecting on the platform, and a thermal barrier coating for covering the gas path surface of platform, and the thermal barrier coating is formed so as to go around from the gas path surface to at least a part of the outer peripheral face of the platform.
In this gas turbine, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the platform of the turbine moving blade can be restrained easily and surely. Therefore, the temperature of combustion gas can be increased, so that the energy efficiency can be enhanced easily.
As defined in claim 10, the present invention provides a gas turbine for producing power by expanding a high-temperature and high-pressure combustion gas-by using a turbine stationary blade and a turbine moving blade, wherein the turbine moving blade comprises a platform, a blade portion erecting on the platform, a shroud provided at the tip end of the blade portion, and a thermal barrier coating for covering a gas path surface extending in the combustion gas flow direction of the shroud, and the thermal barrier coating is formed so as to go around from the gas path surface of shroud to at least a part of the outer peripheral face of the shroud.
In this gas turbine, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the shroud of the turbine moving blade can be restrained easily and surely. Therefore, the temperature of combustion gas can be increased, so that the energy efficiency can be enhanced easily.
As defined in claim 11, the present invention provides a gas turbine for producing power by expanding a high-temperature and high-pressure combustion gas by using a turbine stationary blade and a turbine moving blade, wherein the turbine stationary blade comprises a pair of shrouds each having a gas path surface extending in the combustion gas flow direction, a blade portion held between the shrouds, and a thermal barrier coating for covering the gas path surface of at least either one of the shrouds, and the thermal barrier coating is formed so as to go around from the gas path surface of shroud to at least a part of the outer peripheral face of the shroud.
In this gas turbine, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the shroud of the turbine stationary blade can be restrained easily and surely. Therefore, the temperature of combustion gas can be increased, so that the energy efficiency can be enhanced easily.
As defined in claim 12, the present invention provides a gas turbine for producing power by expanding a high-temperature and high-pressure combustion gas by using a turbine stationary blade and a turbine moving blade, wherein the gas turbine comprises a split ring having a gas path surface extending in the combustion gas flow direction and a thermal barrier coating for covering the gas path surface, which is provided at the outer periphery of the turbine moving blade, and the thermal barrier coating is formed so as to go around from the gas path surface of split ring to at least a part of the outer peripheral face of the split ring.
In this gas turbine, the deterioration and peeling-off of the thermal barrier coating in the vicinity of the peripheral edge portion of the split ring can be restrained easily and surely. Therefore, the temperature of combustion gas can be increased, so that the energy efficiency can be enhanced easily.
As described above, in the gas turbine moving blade, the gas turbine stationary blade, and the gas turbine split ring in accordance with the present invention, the thermal barrier coating is formed so as to go around from the gas path surface of the platform, the shroud, and the split ring body to at least a part of the outer peripheral face. As a result, the deterioration and peeling-off of the thermal barrier coating in the peripheral edge portion of the platform, the shroud, and the split ring body can be restrained easily and surely.
Thereupon, if the above-described gas turbine moving blade, gas turbine stationary blade, or gas turbine split ring is used for a gas turbine, the temperature of combustion gas can be increased, so that the energy efficiency can be enhanced easily.